Apologies, mis-read the forum I was in.
Here are the rules on my 'Downloads' folder :
1 If kind is folder, run rules on folder contents.
2 If date added is not in the last 2 days and kind is folder move folder to trash.
I've also set up a series of different rules for the 'Downloads' folder which move music files, movie files and pictures to other folders on my mac.
Basically everything is working as it should be except Hazel is not moving old folders in 'Downloads' to the trash. For example, I downloaded an episode of family guy to 'Downloads/family guy'. Hazel moved family s08e01.avi to my movies folder but it did not delete 'Downloads/family guy'. In effect I still have to delete the empty folders from 'Downloads' manually.
I got the idea from here:
http://lifehacker.com/320951/set-up-a-s ... with-hazel